Color television systems operate on the additive primary colors red, blue, and green. Tricolor cameras produce signals that represent a scene being viewed in terms of three color-related analog voltages. In order to make color television compatible with monochrome television, a conventional luminance signal is transmitted on a carrier while separate color information is multiplexed onto the carrier for use by color receivers. The luminance signal is obtained by combining the three primary color signals in proportions that take into account the luminosity response of the eye. The actual values were set by the National Television Standards Committee (NTSC) which the later adopted Federal Communications Commission rules specify. The rules specify a luminance signal made up of 59% of the green voltage, 30% of the red voltage, and 11% of the blue voltage (0.59G+0.30R+0.11B). Two color difference signals are specified as the red minus luminance (R-Y) and blue minus luminance (B-Y). The color signals, therefore, are: EQU R-Y=0.70R-0.59G-0.11B (1) EQU b-y=0.89b-0.59g-0.30r (2) EQU y=0.59g+0.30r+0.11b (3)
these color signals are typically matrixed and applied to color subcarrier modulators to be multiplexed with the luminance signal ordinarily transmitted over the television channel.
The conventional way of obtaining the luminance and color difference signals, from the basic red, blue, and green signals, usually involves a matrix circuit having multiple resistor voltage dividers and summing amplifiers. This approach is complicated in that many resistors must be matched and a plurality of amplifiers must be employed. The requirements are difficult to meet in integrated circuit (IC) designs.